Carbohydrates, CH2On

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Carbohydrates, (CH2O)n

• 1. Carbon, hydrogen, oxygen in 121 ratio
• 2. Functions
• 3. Carbon cycle
• 4. Saccharides

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Carbohydrates Functions

• 1. Energy source for most cells, glucose
• 2. Energy storage in plants animals, starch
  glycogen
• 3. Structure for plants, cellulose

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Carbon Cycle

• 1. Respiration- oxidation of glucose to form ATP
  for cellular energy
• 2. Photosynthesis- use of sunlight to change CO2
  H2O into glucose O2

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Saccharides

• 1. Monosaccharides
• 2. Disaccharides
• 3. Polysaccharides

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Monosaccharides

• 1. Unbranched C chain of 3 to 8
• 2. One C is carbonyl group, remaining C atoms
  have -OH groups
• 3. Aldoses ketoses
• 4. Trioses, tetroses, pentoses, hexoses . . .

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Aldose

• 1. First carbon is carbonyl
• glyceraldehyde,
  ribose,
• an aldotriose
  an aldopentose

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Ketose

• 1. Second carbon or . . . is carbonyl
• fructose,
  ribulose,
• a ketohexose a
  ketopentose

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Chiral Carbon

• 1. Carbon with four different atoms or groups
• 2. Chiral carbons form mirror images
• 3. Stereoisomers- compounds with atoms linked in
  same order, but different spatial arrangement
• 4. Enantiomers- stereoisomers that are mirror
  images or chiral

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Chirality Example 1

• 1. Chiral carbon furthest from carbonyl C
  determines D or L
• D-glyceraldehyde L-glyceraldehyde

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Chirality Example 2

• Fischer model
• L-glucose D-glucose

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Biological Monosaccharides

• D-glucose D-galactose
  D-fructose

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D-glucose, dextrose

• 1. Found in fruits, vegetables, honey
• 2. Part of disaccharides sucrose, lactose,
  maltose
• 3. Starch, cellulose, glycogen are polymers of
  glucose
• 4. Blood sugar, 70-90mg/dl, but 130mg/dl after
  meals

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D-galactose

• 1. Part of disaaccharide, lactose, milk sugar,
  gal-glu
• 2. Component of brain nerve cell membranes
• 3. Galactosemia- galactose to glucose enzyme
  missing, cataracts, cirrhosis mental
  retardation, eliminate lactose from diet

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D-fructose, levulose

• 1. Found in fruits honey
• 2. Part of disaccharide, sucrose (table sugar),
  glu-fru
• 3. Converted to glucose in the blood stream

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Cyclic Monosaccharides

• 1. Monosaccharides alternate between chain
  (Fischer) to ring (Haworth)
• 2. C5 -OH reacts with carbonyl carbon to form
  cyclic hemiacetal ring
• 3. Ring is more stable structure most prevalent

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Fructose, chain to ring

• 1. Groups on right of chain are drawn below the
  ring, left to top
• Fischer
  Haworth

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Glucose, chain to ring

• 1. Groups on right of chain are drawn below the
  ring, left to top
• Fischer
  Haworth

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a b Anomers

• 1. C1 -OH may be up or down
• 2. a-D-glucose C1 -OH is down,
• a-amylase in humans allows the digestion of
  starch, a-D-glucose polymer
• 3. b-D-glucose C1 -OH is up, cellulose is
  b-D-glucose polymer cannot be digested by humans

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a b Glucose

• a-D-glucose
  b-D-glucose
• (36) trace
  (64)

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a b Galactose

• a-D-galactose
  b-D-galactose

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a b Fructose

• a-D-fructose
  b-D-fructose

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Aldose Oxidation

• 1. Aldose sugars oxidize to carboxylic acids,
  oxidizing agent is reduced
• 2. Aldose sugars reduce Benedicts soln, CuSO4
  (blue) to Cu2O (red orange
• 3. D-fructose reacts with Benedicts as
  D-glucose, Benedicts drives equilibrium to right

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Benedicts Soln Glucose

• D-glucose D-gluconic
• 
  acid

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Glu-Fru isomerization

• 1. OH- in Benedicts soln causes rearrangement
  at terminal carbon
• D-fructose
  D-glucose
• (ketose)
  (aldose)

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Quantitative Benedicts
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Glycosides

• 1. Cyclic monosaccharides alcohol produce
  acetal or glycoside
• 2. Rxn at hydroxyl group of anomeric C results in
  glycosidic bond
• 3. Bond is a or b depending on which anomer
  reacted
• 4. Glycosidic bond closes ring so mutorotation
  oxidation is no longer possible

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Glucose Glycoside

• 
  methyl-b-D-glucoside

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Disaccharides

• 1. Maltose, glucose glucose
• 2. Lactose, galactose glucose
• 3. Sucrose, glucose fructose

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Maltose

• 1. Malt sugar, barley grains, glucose glucose
• 2. C1 -OH of a-D-gluclose forms glycosidic bond
  with C4 -OH of 2nd a-D-gluclose
• 3. Anomeric C of 2nd glucose can be a or b and
  can open to aldehyde, so maltose is reducing
  sugar

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Maltose Stucture

• a-maltose (a-1,4-glycosidic bond)

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Lactose

• 1. Milk sugar, milk dairy, galactose glucose
• 2. C1 -OH of b-D-galactose forms glycosidic bond
  with C4 -OH of
• a-D-glucose
• 3. Anomeric C of glucose can be a or b and can
  open to aldehyde, so lactose is reducing sugar

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Lactose Structure

• a-lactose (b-1,4-glycosidic bond)

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Sucrose

• 1. Table sugar, sugar cane sugar beets, glucose
  fructose
• 2. C1 -OH of a-D-glucose forms glycosidic bond to
  C2 -OH of b-D-fructose
• 3. Both anomeric C atoms are in bond so neither
  ring can open sucrose is not a reducing sugar

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Sucrose Structure

• sucrose (a,b-1,2-glycosidic bond)

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Fermentation

• 1. Yeast under anaerobic conditions convert
  glucose /or fructose to ethanol
• 2. Invertase splits sucrose or maltose,
  fermenting sugars
• 3. Invertase cannot split lactose, so it is
  nonfermenting sugar

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Blood Type
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Polysaccharides

• 1. Polymers of monosaccharides
• 2. Glucose polysaccharides- plant starches,
  animal starch, cellulose
• 3. Differ in type of glycosidic bonds, number of
  glucose units, amount of branching

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Plant Starch

• Amylose, 20 amylopectin, 80
• Digested by amylase, maltase, HCl

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Amylose

• 1. a-D-glucose units connected by
  a-1,4-glycosidic bonds
• 2. Between 250 to 4000 glucose units in a
  continuous coiled chain

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Amylopectin

• Similar to amylase, but branches about every 25
  glucose units
• a-1,6-glycosidic bond between C6 of main chain
  C1 of branch

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Animal Starch

• 1. Glycogen, stored in liver muscles
• 2. Similar to amylopectin, but branches about
  every 10-15 glucose units
• 3. Same glycosidic bonds as amylopectin

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Cellulose

• 1. Structural material of plants
• 2. Unbranched, parallel chains of glucose
• 3. Glucose units in b-1,4-glycosidic bonds,
  chains hydrogen bond
• 4. Humans lack enzymes to digest
• b -1,4 bonds, some animals have symbiotes that
  can lyse b-1,4 bonds

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Iodine Test

• I2 or I2KI solns are used to test for starches
• Positive result is dark brown to deep blue-black